Semen analysis is an important routine that is extensively practiced in laboratories for evaluating male fertility and preparing artificial insemination. To determine the sperm concentration in semen, the current “gold standard” requires a visual assessment of a sperm sample placed into a counting chamber. The sperm are then manually counted through an optical microscope. Not only that this method is recommended by the World Health Organization (WHO), but also it is widely used in most laboratories that process semen. Due to the labor intensive nature of this manual method, several other optical approaches, including turbidimetry, laser Doppler velocimetry (LDV), and photon correlation spectroscopy have also been proposed to automatically analyze semen. However, these approaches are still not widely adopted partially because they can only provide indirect estimations of the sperm concentration and motility.
Currently, Computer-Assisted Semen Analysis (CASA) systems, which utilize pattern analysis algorithms to automatically process the optical images recorded with a conventional optical microscope, is considered as one of the most promising technologies to replace the traditional manual semen analysis method. An important feature of CASA systems is their ability to provide quantitative information about sperm motility, such as the speed distribution of individual sperm cells, which has been proven to be rather important for predicting fertilization rate as well as for evaluation of the correlation between various drugs and sperm quality. However, despite the fact that state-of-the-art CASA systems are very efficient and versatile, their relatively large dimensions, high cost and maintenance needs partially hinder their wide-spread use in fertility clinics. For the same reason, application of this platform to field-use in veterinary medicine such as stud farming and animal breeding has also been significantly limited.
In addition to these, commercially available male fertility test kits for personal home use, such as FertilMARQ (U.S. Pat. Nos. 5,895,749 and 5,935,800) or SpermCheck, also aim to indirectly quantify sperm concentration by a color change due to chemical staining or labeling of sperm-specific proteins. These tests, however, cannot quantify sperm motility or the concentration of motile sperm. Recently, an alternative semen analysis platform involving a compact micro-fluidic device that can measure electrical impedance changes due to sperm movement has also been reported. See Segerink, L. I. et al., On-chip determination of spermatozoa concentration using electrical impedance measurements, Lab Chip 2010, 10, 1018-1024. However, this lab-on-a-chip platform can only provide the total number of the sperm in the sample and cannot differentiate motile and immotile sperm from each other, which is an important limitation.